The goal of this project is to demonstrate that direct registration of endoscopic video to pre-operative CT is a viable route to increasing the precision and usefulness of current surgical navigation systems. These results will set the stage for developing new approaches to high precision intra-operative navigation and visualization in anterior skull surgery. This exploratory application is specifically focused on developing and evaluating image-based structure and motion recovery algorithms and video/CT registration algorithms on a representative class of specimens. Working closely with our physician collaborator, we will perform algorithm development and validation according to the following specific aims: 1. Specific Aim 1: Compute surface structure from endoscopic images. Implement and evaluate algorithms for computing the motion of the endoscope and the geometric structure of the surrounding tissue from sequences of images. Evaluate the accuracy of motion and structure data against ground truth models. 2.Specific Aim 2: Registration of pre-operative CT to endoscopic images. Implement and evaluate algorithms for registering the three-dimensional (3D) endoscope data of specific aim 1 with surfaces segmented from pre-operative CT images. Evaluate the reliability and accuracy of this registration process. 3. Specific Aim 3: Accuracy evaluation against current surgical navigation systems: Perform tests on an animal cadaver model to evaluate the accuracy of endoscopic registration in realistic circumstances, and compare that accuracy with existing surgical navigation systems. This exploratory/developmental application sets the stage for new clinical treatments enabled by high- precision navigation and visualization. It also will provide the basis for highly accurate, intra-operatively updated surface models of the surgical field, new methods of intra-operative measurement, and possibly tracker-free navigation systems. [unreadable] [unreadable] [unreadable]